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The mechanics of nectar offloading in the bumblebee Bombus terrestris and implications for optimal concentrations during nectar foraging.

Accepted version
Peer-reviewed

Type

Article

Change log

Authors

Pattrick, Jonathan G 
Symington, Hamish A 
Glover, Beverley J 

Abstract

Nectar is a common reward provided by plants for pollinators. More concentrated nectar is more rewarding, but also more viscous, and hence more time-consuming to drink. Consequently, theory predicts an optimum concentration for maximizing energy uptake rate, dependent on the mechanics of feeding. For social pollinators such as bumblebees, another important but little-studied aspect of foraging is nectar offloading upon return to the nest. Studying the bumblebee Bombus terrestris, we found that the relationship between viscosity (µ) and volumetric transfer rates (Q) of sucrose solutions differed between drinking and offloading. For drinking, Q ∝ µ-0.180, in good agreement with previous work. Although offloading was quicker than drinking, offloading rate decreased faster with viscosity, with Q ∝ µ-0.502, consistent with constraints imposed by fluid flow through a tube. The difference in mechanics between drinking and offloading nectar leads to a conflict in the optimum concentration for maximizing energy transfer rates. Building a model of foraging energetics, we show that including offloading lowers the maximum rate of energy return to the nest and reduces the concentration which maximizes this rate by around 3%. Using our model, we show that published values of preferred nectar sugar concentrations suggest that bumblebees maximize the overall energy return rather than the instantaneous energy uptake during drinking.

Description

Keywords

flow rate, honeypots, nectar, offloading, sucrose, viscosity, Animals, Bees, Plant Nectar, Viscosity

Journal Title

J R Soc Interface

Conference Name

Journal ISSN

1742-5689
1742-5662

Volume Title

17

Publisher

The Royal Society

Rights

All rights reserved
Sponsorship
Biotechnology and Biological Sciences Research Council (BB/J014540/1)
BBSRC (1943281)
This work was supported by a Biotechnology and Biological Sciences Research Council PhD Studentship under grant BB/J014540/1 to J.G.P.